The purpose of this study is to further define what percentage of individuals with a positive history and skin test will react on a challenge sting, along with the question of whether a single sting is adequate. Another aspect of this study involves an attempt to determine parameters predictive of a reaction, so that challenge stings are no longer necessary. Most of these will be laboratory studies, which require only the drawing of blood. In conclusion, the benefits of this study are to monitor these reactions in a controlled clinical setting, to develop more accurate markers for insect sting allergy to detect the individuals who are susceptible to severe reactions, and to avoid unnecessary therapy in many patients.